ANCIENT WATER LEVELS OF CH A MPLAIN— HUDSON VALLEYS 87 



Chapter 2 



RETREAT OF THE WISCONSIN ICE SHEET FROM EAST- 

 ERN NEW YORK 



In this and the following chapters which deal with the evidences 

 of the retreat of the ice sheet from the Hudson and Champlain 

 valleys, the aim has been rather to determine the conditions of 

 the drainage and water levels at the front of the ice sheet than to 

 attempt a presentation of a full account of the successive stages 

 of the ice retreat. Many additional facts, such as are presented 

 here, concerning gravels and sands deposited about the ice margin 

 in the Hudson and Champlain valleys remain to be described and 

 located on maps. 



The data concerning water levels derived from deposits made at 

 successive stages in the retreat of a glacier must necessarily per- 

 tain to a series of water bodies whose levels may or may not have 

 been permanent as the water extended itself into the area aban- 

 doned by the retreat of the ice front. 



In relation to the very beginning of the ice retreat, there are two 

 classes of evidence bearing on the position of sea level at the 

 mouth of the Hudson river, one of these categories of fact lies 

 outside the glaciated area, the other lies inside that field and 

 forms the body of matter with which we are concerned. 



Extraglacial evidence of water levels. At the time of the culmi- 

 nation of the late Wisconsin epoch when the ice sheet stood far- 

 thest south and at New York Narrows, the question arises whether 

 the sea was where it now is, or whether the land stood higher or 

 lower in relation to sea level. Of the geologic evidence outside of 

 the glacial deposits of this epoch, there are three localities within 

 a few miles of New York city which were examined critically with 

 reference to this question. These localities comprise the vicinity 

 of Cheesequake creek, on the Monmouth county shore of New Jer- 

 sey, the small unglaciated area of Staten Island N. Y., and the 

 ridge which extends through Far Rockaway on Long Island N. Y. 



Terrace at mouth of Cheesequake creek, Monmouth county, N. J. 

 Cheesequake creek occupies a valley about 2y 2 miles long and 

 with an average width of 1 mile from near its mouth on the beach 

 of Raritan bay to its head. Except for small streams entering 

 on the northwest near its mouth and on its eastern side from the 



